1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a color filter substrate of an LCD device.
2. Discussion of the Related Art
Among various ultra-thin flat type display devices, which include a display screen having the thickness of several centimeters (cm), a liquid crystal display (LCD) device attracts great attentions in that it has advantages such as low power consumption due to low driving voltage and portability. In this respect, the LCD device can be widely used for notebook computers, monitors, aircraft, and etc.
Generally, the LCD device includes a thin film transistor (TFT) substrate, a color filter substrate, and a liquid crystal layer. The TFT substrate is positioned opposite to the color filter substrate with a predetermined interval therebetween, and the liquid crystal layer is formed between the TFT substrate and the color filter substrate. In this state, the alignment of liquid crystal molecules of the liquid crystal layer changes based on an applied voltage, whereby the picture image is realized according to the control on transmissivity of light.
On the TFT substrate, a plurality of gate lines are arranged in a first direction at fixed intervals, a plurality of data lines are arranged in a second direction perpendicular to the gate lines also at fixed intervals, a plurality of pixel electrodes in respective pixel regions defined by the gate lines and the data lines in a matrix-type configuration, and a plurality of thin film transistors (TFTs) switchable in response to signals on the gate lines for transmission of signals on the data line to the pixel electrodes.
The color filter substrate has a light-shielding layer having light-shielding patterns for shielding light from regions other than the pixel regions, and a color filter layer having color filter patterns of red (R), green (G) and blue (B) corresponding to the respective pixel regions between each of the light-shielding patterns, for displaying the colors.
According to an operation mode of the LCD device, a common electrode or an overcoat layer may be additionally formed on the light-shielding layer and the color filter layer. For a TN (Twisted Nematic) mode LCD device, the common electrode is required. For an IPS (In-Plane Switching) mode LCD device, the overcoat layer is required. With the IPS mode LCD device, the common electrode is formed on the thin film transistor substrate.
Hereinafter, a related art color filter substrate will be described with reference to the accompanying drawings.
FIGS. 1A to 1E are cross sectional views of the process for fabricating a color filter substrate according to the related art.
First, light-shielding patterns 12a are formed on a glass substrate 10 by photolithography (FIGS. 1A to 1C), and each of color filter patterns 16 of R, G and B is formed between the light-shielding patterns 12a by photolithography (FIG. 1D). Then, a common electrode or an overcoat layer 18 is formed on an entire surface of the glass substrate 10 (FIG. 1E).
The detailed process will be explained as follows.
As shown in FIG. 1A, a light-shielding material 12, an opaque photosensitive light-shielding material, is coated on the glass substrate 10.
Referring to FIG. 1B, a mask 14 of a desired predetermined pattern is positioned above the glass substrate 10 having the light-shielding material 12 and the light is irradiated thereon.
As shown in FIG. 1C, the light-shielding material 12 irradiated with the light is developed and cured, thereby forming the light-shielding patterns 12a. 
As shown in FIG. 1D, each of the color filter patterns of R, G and B 16 is formed between the light-shielding patterns 12a. The color filter patterns 16 as well as the light-shielding patterns 12a are formed by photolithography.
Referring to FIG. 1E, the common electrode (in case of the TN mode LCD device) or the overcoat layer (in case of the IPS mode LCD device) 18 is formed on the color filter patterns 16, thereby completing the color filter substrate according to the related art.
However, the method for fabricating the color filter substrate according to the related art has the following disadvantages.
In the color filter substrate according to the related art, a step coverage is generated on both sides of each of the color filter patterns 16 due to the light-shielding patterns 12a, whereby it cause a deterioration of the picture quality.
Prior to forming the color filter patterns 16, the step coverage is formed due to the light-shielding patterns 12a. Thus, when the color filter patterns 16 are formed, it is difficult to use a relatively simple spinless coating method. Instead of the spinless coating method, a relatively complex photolithography process is used to form the color filter patterns 16.
Also, it is necessary for the light-shielding patterns 12a to be a predetermined thickness suitable to shield the light. If the photolithography process using opaque light-shielding material is performed, as shown in FIG. 1C, the entire thickness of each of the light-shielding patterns 12a is not uniform. That is, the ends of each of the light-shielding patterns 12a are relatively thinner than the central portion of each of the light-shielding patterns 12a. Accordingly, it is impossible to completely shield the light, thereby lowering the luminance.